Thermoelectric wristwatches using thermoelectric for elements producing electromotive force based on the Seebeck effect as an energy source instead of or as a supplement to batteries have been disclosed.
FIG. 2 is a cross-sectional view showing the structure of the prior art thermoelectric timepiece using electrothermic elements as an energy source.
The thermoelectric timepiece is a timepiece structure comprising a movement 201, a thermoelectric generator 202, an electrical energy storage device (not shown), a metallic bottom portion 203, a frame portion 204 made of a thermally insulating material, and a metallic top portion 205. An electrothermic wristwatch of the construction described thus far is disclosed, for example, in Japanese Patent Publication No. 13279. However, thermoelectric generator units which have sufficient capability to generate power and are designed, taking miniaturization into account, have not been put into practical use. Also, electrothermic timepieces using such thermoelectric generator units have not been put into practical use. In addition, details of the structure of this thermoelectric generator unit are not disclosed.
An electrothermic element can produce an electromotive force in response to a temperature difference between a heat-absorbing side that is a first support member and a heat-dissipating side that is a second support member. As the temperature difference increases, the electromotive force increases. When one attempts to obtain a large electromotive force, the efficiency of absorption of heat from the heat source and the efficiency of dissipation of heat from the electrothermic element should be enhanced. For this purpose, it is necessary to secure a highly efficient thermally conductive path for conducting heat from the rear cover to the electrothermic element efficiently and for dissipating heat from the electrothermic element to the case body and to the outside air.
However, electrothermic elements are vulnerable to external forces. Especially, n- and p-type semiconductors take the form of elongated pillars and are arrayed vertically in large quantities. Therefore, if a lateral force or excessive vertical force is applied relative to the direction of conduction of heat through the n- and p-type semiconductors, there arises a danger of destruction of the electrothermic elements. Consequently, sufficient force cannot be applied when the heat-absorbing member, the heat-dissipating member, and the electrothermic elements are brought into contact with each other and thus it has been impossible to improve the efficiency of heat conduction.
Where heat from an arm that becomes a heat source should be efficiently taken into the electrothermic elements, it is desired that the electrothermic elements be placed on the rear cover of the time piece. Where the ease of assembly and disassembly of the electrothermic timepiece is taken into account, connector structures for connection of the output terminals of the electrothermic elements with a step-up charging circuit and a secondary cell mounted in the body of the timepiece cannot be easily accomplished.
To improve the efficiency of power generation, it is desired that pressure be applied to lower the thermal contact resistance of members used for absorbing and dissipating heat from the electrothermic element or thermoelectric generator unit with the heat source or heat-dissipating means. However, materials having good thermal conductivities typically have low elastic module and sufficient force cannot be applied. Hence, the thermal contact is unstable.
Accordingly, it is an object of the present invention to provide a structure that prevents electrothermic elements from being destroyed due to external force, facilitates connection of the output terminals of thermoelectric generator units with a step-up charging circuit and with a secondary battery, and offers good efficiency of thermal conduction.